Device for imaging and observing an eye at a selectable image scale

ABSTRACT

The present invention is directed to a device for examining the eye, preferably the fundus of the eye, by an optical system and electronic sensors for image recording in different imaging scales. In the device according to the invention, at least two image recording sensors with different shape factors are swivelably arranged in the imaging plane of the device. These image recording sensors have optically active surfaces of different geometric sizes, an approximately identical number of pixels and preferably the same electronic control and evaluation. The invention described herein requires no additional objectives and the optical adjustment is limited to an individual rigid objective. An exact alignment of the image recording sensors in the imaging plane and manufacturing tolerances can be compensated by adapting the image section by means of software. It is particularly advantageous that the imaging scale is influenced without changing the optical parameters of the system.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority of International Application No.PCT/EP2004/005767, filed May 28, 2004, and German Application No. 103 26510.4, filed Jun. 6, 2003, the complete disclosures of which are herebyincorporated by reference.

BACKGROUND OF THE INVENTION

a) Field of the Invention

The present invention is directed to a device for examining the eye,preferably the fundus of the eye, by means of an optical system andelectronic sensors for image recording, wherein sectional enlargementsof the recordings are possible by means of changing the imaging scale.

b) Description of the Related Art

According to the known prior art, the imaging scale in devices of thetype mentioned above is usually changed by optical means which areswiveled into and out of the beam path in addition to or in exchangewith one another.

The Laid Open Application DE 24 35 548 describes an optical system forphotographing the retina with selectable imaging scale in which aplurality of optical changing systems which can be introduced into thebeam path individually are provided in addition to the stationaryobjective systems. These changing systems are axially displaceabletogether with the aperture diaphragm in order to carry out focusing foreyes with defective vision. This technical solution is realized, forexample, in the “FF 450” fundus camera by Carl Zeiss Meditec AG.

The disadvantage of this application consists primarily in thecomplicated adjustment of the optics and in the fact that the mechanicalmovement must be carried out very exactly. Since a complete set ofoptical components is required for every imaging scale, the structuralsize of the device in its entirety is substantially influenced by thesize of the objective turret.

A simple technical solution for digital observation and documentation ofthe ocular fundus without eyepieces is offered by the “VISUCAM lite”fundus camera by Carl Zeiss Meditec AG. In this fundus camera, ablack-and-white sensor and a color sensor are alternately laterallyswiveled into the imaging plane of the system. In addition to the colorphotographs, black-and-white photographs are made using differentmonochrome techniques (red-free, blue, red) due to a higher sensitivity.To facilitate their comparison, the sensors have identical shapefactors. By virtue of its many-sided possibilities for recording,analysis and aftertreatment, this solution provides a basic instrumentfor ophthalmologic practice and laser treatment.

The disadvantage in this device is that it does not provide for changingthe optical imaging scale. In order to achieve this, an additionalobjective turret would be required. A correction of defective vision(also referred to as focusing) is carried out by a mechanical movementof the sensors along the optical axis.

OBJECT AND SUMMARY OF THE INVENTION

It is the primary object of the present invention to develop a solutionfor displaying and observing an eye in which imaging scales areselectable without making the basic construction of the device overallsubstantially more complicated and bulky. Further, the effort requiredfor adjustment and assembly is minimized.

According to the invention, this object is met by a device fordisplaying and observing an eye with selectable imaging scale comprisingimage recording sensors with different shape factors which areswivelably arranged in an imaging plane.

With the proposed technical solution, image sections of the eye and ofthe fundus of the eye in particular can be observed and documented indifferent sizes.

The invention will be described in the following with reference to anembodiment example.

BRIEF DESCRIPTION OF THE DRAWING

In the drawing:

FIG. 1 shows the basic construction of the device according to theinvention in a fundus camera.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the device according to the invention for displaying and observing aneye with selectable imaging scale, at least two image recording sensorswith different shape factors are swivelably arranged in the imagingplane of the device.

The different shape factors can be realized by optically active surfacesof the image recording sensors of identical geometrical size with adifferent quantity of pixels. The image recording sensors which areswivelably arranged in the imaging plane preferably have anapproximately identical numbers of pixels with optically active surfacesof different sizes. This has the advantage that the electronic controland evaluation for the image recording sensors are identical.

The image recording sensors arranged in the imaging plane can beintroduced into the beam path by a lateral movement as well as by acircular movement. The cable feed is considerably simplified in the caseof a lateral movement.

FIG. 1 shows the basic construction of the device according to theinvention. In the illumination beam path, the light coming from thelight source 1 is guided to the ocular fundus 7 via the illuminationoptics 2, the diaphragm for the annular illumination aperture 3, thepinhole mirror 4, the ophthalmoscope lens 5 and the eye lens 6. Thefundus 7 which is illuminated in this way is imaged in the imaging plane9 via the ophthalmoscope lens 5 through the pinhole mirror 4 via theprincipal objective 8. According to the invention, at least twoswivelable image recording sensors 10.1 and 10.2 are arranged in theimaging plane 9 on a common carrier 11. In the imaging beam path, afirst intermediate image 12 is generated between the ophthalmoscope lens5 and the pinhole mirror 4 and a second intermediate image 13 isgenerated in the imaging plane 9. This imaging plane 9 is located at avariable distance from the main objective 8 depending on the defectivevision of the eye being examined. Focusing is necessary in order toachieve a sharp image on one of the image recording sensors 10.1 or10.2. Focusing is carried out by axial displacement of the carrier 11 sothat one of the image recording sensors 10.1 or 10.2 is located in theimaging plane 9. The different magnification steps for display andobservation are realized by swiveling in another image recording sensor10.1 or 10.2.

The change in the imaging scale is carried out by means of swivelingimage recording sensors with different shape factors into the imagingplane of the ophthalmic instrument. The image recording sensors have anapproximately identical number of pixels, but have optically activesurfaces of different geometric sizes. Accordingly, the imaging scale isinfluenced without changing the optical parameters of the system.

No additional objectives are required for this purpose in the describedinvention. The optical adjustment is limited to an individual rigidobjective. Precise mechanical guidance and the movement of a pluralityof objectives are no longer necessary. Even an exact alignment of theimage recording sensors in the imaging plane is not absolutely necessarybecause they can be compensated by adapting the image section by meansof software. This also applies to manufacturing tolerances.

It is particularly advantageous that the imaging scale is influencedwithout changing the optical parameters of the system. Accordingly,image sections of the eye and of the fundus of the eye can be observed,recorded, reworked and stored in different sizes.

While the foregoing description and drawings represent the presentinvention, it will be obvious to those skilled in the art that variouschanges may be made therein without departing from the true spirit andscope of the present invention.

1. A device for displaying and observing an eye with selectable imagingscale, comprising a plurality of image recording sensors with differentshape factors being swivelably arranged in an imaging plane forrecording images in a single beam path.
 2. The device according to claim1, wherein the image recording sensors which are swivelably arranged inthe imaging plane have an approximately identical number of pixels andoperated by the same electronic control and evaluation unit.
 3. Thedevice according to claim 1, wherein the image recording sensorsarranged in the imaging plane are introduced into a beam path by alateral movement.
 4. The device according to claim 1, wherein the imagerecording sensors arranged in the imaging plane are introduced into abeam path by a circular movement.